Alterations in IgG subclasses in acquired immune deficiency syndrome.

Decreased IgG subclass levels in pyogenic infections and immunocompromised situations have been described. A study was made to determine IgG subclass levels in four groups of 68 Hispanic patients. The first group consisted of 25 terminal patients with AIDS, the second group of 20 i.v. drug abusers, and the third group of eight hospital patients with neither a diagnosis of AIDS/ARC nor a history of i.v. drug abuse. IgG subclass levels of these 53 cases were compared with those of a fourth group of 15 normal controls. The total IgG, IgA, and IgM levels as well as the four IgG subclass concentrations were measured by radial immunodiffusion using appropriate standards and specific antisera. The first two groups had similar values, with an average IgG level of 10.37 g/liter; IgA, 2.68; and IgM, 1.78; subclass levels were IgG1, 6.68 g/liter; IgG2, 2.77; IgG3, 0.34; and IgG4, 0.68. These were significantly lower than those of controls, except for IgG4. Determination of minor subclasses may offer some possibilities for immunomodulation and therapy and could be useful in terms of prognosis.